Let’s talk about TMVs
Overview
Thermostatic Mixing Valves, or “TMVs” are utilised where there is a danger from scalding. A scald is defined as “damage to the skin caused by heat and by something wet, such as hot water or steam”. The TMV blends hot and cold water to produce water at a safer temperature.
The exposure times at which hot water can cause third degree burns to healthy adult skin is as follows:
- 30 seconds at 55°C
- 5 seconds at 60°C
- <1 second at 70°C
Children, the elderly, those with skin conditions or sensory impairment are less likely to react quickly to prevent skin damage. There is obviously a high percentage of people within these groups in healthcare and education premises and numerous TMVs will be fitted here.
BUT! Where they are fitted, they can cause problems:
The pros and cons of thermostatic mixing valves:
| Pros | Cons |
| Reduce risks from scalds | Extra installation and commissioning costs |
| Provide convenient warm water | Require regular maintenance |
| Failsafe testing | |
| Strainer/filter cleaning | |
| Disinfection | |
| Disruption whilst carrying out works | |
| Crossover issues | |
| Expensive |
What are the alternatives?
Removing them should be the first consideration – “Where the scalding risk is identified as insignificant, TMVs are not required” – HSG 274 Part 2 Paragraph 2.75. Where thermostatic control is still required then consider using, lower risk, lower maintenance alternatives such as:
- Sequential mixer
- Normal mixer outlet
- Intelligent outlet
- Thermostatic mixer tap
If you would like more information on scald risk assessments, TMV management or any other legionella control or water system safety issue then please contact us using the “Send Message” form at the bottom of the page ↓